Led indicator lamp

ABSTRACT

An LED indication lamp having desired luminous intensity distribution characteristics without need for any light-emitting diode of special shape. The LED indication lamp comprising a plurality of light-emitting diodes and having specified luminous intensity distribution characteristics is further provided with a condenser lens. The light-emitting diodes are arranged in a pattern corresponding to a luminous intensity distribution pattern determined according to the luminous intensity distribution characteristics. The light-emitting diodes thus arranged and the condenser lens are arranged so that the light emitted from the light-emitting diodes in the luminous intensity distribution pattern through the condenser lens satisfies the luminous intensity distribution characteristics.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an LED indicator lamp,particularly to an LED indicator lamp used in traffic signals.

[0003] 2. Description of the Related Art

[0004] As light emitting diodes capable of emitting light of R, G and Bprimary colors and light emitting diodes capable of emitting white lightwith high luminance have been developed, LED indicator lamps constitutedfrom a plurality of light emitting diodes arranged in an array have beenput in use for various applications. The LED indicator lamp has a farhigher service life than that of an incandescent lamp, and also shows ahigh efficiency and a high resistance against vibration. For theseadvantages, the LED indicator lamp has been used in advertising signboards, traffic sign boards displaying route guide or trafficinformation, light source for traffic signals and large screens.

[0005] With regards to the application to traffic signals, inparticular, while the incandescent lamp used as the light source of theconventional traffic signal requires large reflector mirrors and colorfilters, the LED indicator lamp has such advantages as the capability toemit light of a single color that eliminates the need for a color filterand the capability to emit light with some degree of directivity thateliminates the need to install a large reflector mirror.

[0006] Moreover, a traffic signal constituted from LEDs that does notneed reflector mirrors and color filters also has an advantage of beingfree from spurious lighting that is caused by extraneous light that hasentered the traffic light and reflected on the reflector mirror placedbehind an incandescent lamp comes out of the traffic signal through acolor filter.

[0007] A constitution of a traffic signal using light emitting diodes isdisclosed in U.S. Pat. No. 6,019,493 wherein a high efficiency lightemitting element capable of uniform light emission is constituted byproviding a lens made by integrally forming a central convex lens and aplurality of annular convex lenses located around the central convexlens.

[0008] International Patent Application PCT/IB97/01974 (InternationalPublication No. WO98/16777) discloses an LED indicator lamp that has aconvex lens (Fresnel lens) placed in front thereof and a plurality oflight emitting diodes distributed densely around the optical axis sothat failure of one of the light emitting diodes does not causesignificant change in the light intensity distribution.

[0009] The LED indicator lamp used in traffic signals and sign boards isusually installed at overhead height so as to be recognized by manypeople from a distance. As such, the LED indicator lamp is required toemit light with horizontally symmetrical intensity distribution butasymmetrical intensity distribution in vertical direction so that lightintensity is higher in the front field and the lower field.

[0010] As it has been made possible to increase the luminous intensityof light emitting diodes recently, it is enabled to decrease the numberof light emitting diodes required in an LED indicator lamp.

[0011] However, a new problem has arisen that it is difficult to achieveplanar light emission of uniform intensity with an LED indicator lampconsisting of a small number of light emitting diodes that have highluminous intensity.

SUMMARY OF THE INVENTION

[0012] An object of the present invention is to provide an LED indicatorlamp that is capable of achieving planar light emission of uniformintensity and a desired luminous intensity distribution characteristic.

[0013] In order to achieve the object described above, a first LEDindicator lamp of the present invention has a predetermined luminousintensity distribution characteristic comprising a plurality of lightemitting diodes and a condenser lens, wherein the plurality of lightemitting diodes are arranged in a pattern that corresponds to a luminousintensity distribution pattern that is set according to the luminousintensity distribution characteristic described above, while the lightemitting diodes and the condenser lens are arranged so that the luminousintensity distribution characteristic is achieved by the light that isemitted by the plurality of light emitting diodes and output through thecondenser lens in the luminous intensity distribution pattern.

[0014] The first LED indicator lamp of the present invention that isconstituted as described above can achieve planar light emission ofuniform intensity, since the light emitted by the plurality of lightemitting diodes is viewed through the condenser lens.

[0015] With the constitution described above, a desired luminousintensity distribution pattern can be easily formed since the luminousintensity distribution pattern is determined by the combination of thearrangement pattern of the plurality of light emitting diodes and therelative positions of the light emitting diodes and the condenser lens.

[0016] In this specification, the term luminous intensity distributioncharacteristic is used in a broader sense than luminous intensitydistribution pattern and includes luminous intensity distributionpattern.

[0017] The luminous intensity distribution pattern determined accordingto luminous intensity distribution characteristic means, for example, aluminous intensity distribution pattern that is suitable for achievingthe luminous intensity distribution characteristic and, in case theluminous intensity distribution characteristic is represented by aparticular luminous intensity distribution pattern, means the luminousintensity distribution pattern itself.

[0018] Moreover, an arrangement pattern that corresponds to a luminousintensity distribution pattern means an arrangement pattern that, incombination with one or more other element, can achieve the luminousintensity distribution pattern.

[0019] In the first LED indicator lamp of the present invention, theplurality of light emitting diodes are preferably located at the focusof the condenser lens or in the vicinity thereof.

[0020] Also in the first LED indicator lamp of the present invention,the plurality of light emitting diodes may be arranged on a plane thatcrosses the optical axis at right angles at the focus of the condenserlens or in the vicinity thereof.

[0021] Also in the first LED indicator lamp of the present invention,the plurality of light emitting diodes may be arranged on a plane thatcrosses the optical axis obliquely at the focus of the condenser lens orin the vicinity thereof.

[0022] Such a constitution as described above makes it possible tochange the luminous intensity distribution pattern in accordance to theangle between the plane and the optical axis.

[0023] Also in the first LED indicator lamp of the present invention,the plurality of light emitting diodes may be distributed in athree-dimensional arrangement at the focus of the condenser lens or inthe vicinity thereof.

[0024] This constitution makes it possible to form the luminousintensity distribution pattern in accordance to the three-dimensionalarrangement of the light emitting diodes.

[0025] In the first LED indicator lamp of the present invention, thecondenser lens is preferably a Fresnel lens that can be made thin andlight in weight.

[0026] Also in the first LED indicator lamp of the present invention,the plurality of light emitting diodes may be disposed in such anarrangement as the number of light emitting diodes located above theoptical axis is larger than the number of light emitting diodes locatedbelow the optical axis, which enables it to direct light with higherintensity downward than upward.

[0027] In this specification, the words up and down refer to the upperand lower positions in a setup where the LED indicator lamp is used.

[0028] Also in the first LED indicator lamp of the present invention,the plurality of light emitting diodes may be disposed in such anarrangement as the light emitting diodes are distributed in one portionwith a density different from that in other portions.

[0029] This constitution makes it possible to change the light intensitydepending on the direction through varying density of the light emittingdiodes.

[0030] Furthermore, in the first LED indicator lamp of the presentinvention, the plurality of light emitting diodes may include lightemitting diodes that are intended to correct unevenness in the lightintensity distribution of the luminous intensity distribution patternproduced by the light emitted through the condenser lens.

[0031] Also in the first LED indicator lamp of the present invention,the plurality of light emitting diodes may be disposed in such anarrangement as the light emitting diodes are placed in at least oneportion at intervals different from the intervals between light emittingdiodes in other portion.

[0032] This constitution makes it possible to change the light intensitydistribution in the luminous intensity distribution pattern throughvarying intervals between the light emitting diodes.

[0033] The first LED indicator lamp of the present invention may alsohave a translucent cover placed in front of the condenser lens.

[0034] The translucent cover preferably has a lens pattern formedthereon so as to smooth out the periodic intensity distributiongenerated by the periodic arrangement of the light emitting diodes.

[0035] A second LED indicator lamp of the present invention has apredetermined luminous intensity distribution characteristic comprisinga plurality of light emitting diodes, a condenser lens placed in frontof the plurality of light emitting diodes and a translucent cover with alens pattern formed thereon being placed in front of the condenser lens,wherein the plurality of light emitting diodes are arranged in a patternthat corresponds to a luminous intensity distribution pattern that isset according to the luminous intensity distribution characteristicdescribed above, while the light emitting diodes, the condenser lens andthe translucent cover are arranged so that the luminous intensitydistribution characteristic is achieved by the light that is emitted bythe plurality of light emitting diodes through the condenser lens andthe translucent cover in the luminous intensity distribution pattern.

[0036] The second LED indicator lamp of the present invention that isconstituted as described above can achieve the luminous intensitydistribution characteristic by means of the translucent cover inaddition to the light emitting diodes and the condenser lens, andtherefore makes it possible to form a luminous intensity distributionpattern that is difficult to form with only the light emitting diodesand the condenser lens, thereby satisfying broader requirements.

[0037] In the second LED indicator lamp of the present invention, thelens pattern formed on the translucent cover preferably formed so as tosmooth out the periodic intensity distribution generated by the periodicarrangement of the light emitting diodes and make the luminance uniformover the light emitting plane.

BRIEF DESCRIPTION OF THE DRAWINGS

[0038]FIG. 1 is an exploded perspective view showing the constitution ofLED indicator lamp according to an embodiment of the present invention.

[0039]FIG. 2 is a plan view schematically showing the arrangement oflight emitting diodes in the LED indicator lamp of the embodiment.

[0040]FIG. 3A is a plan view showing the inner surface of a lens patternof a translucent cover according to the embodiment.

[0041]FIG. 3B is a perspective view showing the inner surface of a lenspattern of a translucent cover according to the embodiment.

[0042]FIG. 4 through FIG. 8 schematically show luminous intensitydistribution patterns corresponding to the arrangement of the lightemitting diodes.

[0043]FIG. 9 is a graph showing an example of luminous intensitydistribution characteristic according to the embodiment.

[0044]FIG. 10 is a plan view showing the arrangement of light emittingdiodes in the LED indicator lamp of a variation of the presentinvention.

[0045]FIG. 11A is a plan view showing the arrangement of light emittingdiodes in a variation of the present invention different from that ofFIG. 10.

[0046]FIG. 11B is a graph schematically showing the intensitydistribution as a function of angle in the case of arranging the lightemitting diodes as shown in FIG. 11A.

[0047]FIG. 12A is a diagram schematically showing an image formed on animaginary screen when two light emitting diodes are placed on a planeperpendicular to the optical axis of the condenser lens 3.

[0048]FIG. 12B is a schematic diagram showing a constitution when twolight emitting diodes are placed on a plane perpendicular to the opticalaxis of the condenser lens 3.

[0049]FIG. 13A is a diagram schematically showing an image formed on animaginary screen when two light emitting diodes are placed on a planethat is inclined against the optical axis of the condenser lens 3.

[0050]FIG. 13B is a schematic diagram showing the constitution when twolight emitting diodes are placed on a plane that is inclined against theoptical axis of the condenser lens 3.

[0051]FIG. 14A is a diagram schematically showing an image formed on animaginary screen when a plurality of light emitting diodes are disposedin three-dimensional arrangement shown in FIG. 14B.

[0052]FIG. 14B is a schematic diagram showing an example of inthree-dimensional arrangement of a plurality of light emitting diodes.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0053] Now the LED indicator lamp according to an embodiment of thepresent invention will be described below.

[0054] The LED indicator lamp of the present invention is an LEDindicator lamp comprising a casing 2 of truncated conical shape that hasa round bottom surface and an opening having larger diameter than thatof the bottom surface, an LED assembly 1 having a plurality of lightemitting diodes 11, 11 a disposed on a substrate 12 placed at the bottomof the casing 2, a condenser lens 2 located at the opening of the casing2 and a translucent cover 4 located at the opening of the casing 2 so asto cover the condenser lens 3, so that light is emitted in apredetermined luminous intensity distribution pattern.

[0055] In more detail, the condenser lens 3 of the LED indicator lamp ofthe present invention is a Fresnel lens that has the function of aconvex lens where light incident on one plane thereof exits from theplane on the other side and is focused, and is placed at the opening ofthe casing 2 so that center of the lens substantially corresponds withthe opening of the casing 2.

[0056] The LED assembly 1 of this embodiment is made by placing theplurality of light emitting diodes 11, 11 a on the substrate 12 in suchan arrangement as described below.

[0057] In the LED assembly 1, the plurality of light emitting diodes 11are disposed on the substrate 12 so as to constitute a fundamentalarrangement pattern 13 corresponding to a luminous intensitydistribution pattern that satisfies a luminous intensity distributioncharacteristic required of the LED indicator lamp, as shown in FIG. 2.

[0058] The light emitting diode 11 a is provided to correct the luminousintensity distribution pattern or the light intensity distributiongenerated by the fundamental arrangement pattern 13 so as to form aluminous intensity distribution pattern generated through the condenserlens 3 approximate to the desired luminous intensity distributionpattern or to smooth out the unevenness in the intensity distribution,and is placed at a predetermined position in the vicinity of thefundamental arrangement pattern 13.

[0059] In the LED assembly 1 of this embodiment, the fundamentalarrangement pattern 13 is formed so as to comply with a rule thatcorresponds to the desired luminous intensity distribution pattern.

[0060] More specifically, the fundamental arrangement pattern 13 of thisembodiment is such that the light emitting diodes are disposed along aplurality of horizontal lines parallel to reference horizontal linesthat are perpendicular to the optical axis of the condenser lens 3,while the number of light emitting diodes disposed on one horizontalline is made larger on the horizontal line located higher.

[0061]FIG. 2 shows that the number of light emitting diodes disposed onone horizontal line is one more than the number of light emitting diodesdisposed on the horizontal line located just below. However, the presentinvention is not limited to this constitution, and any arrangement ofthe light emitting diodes 11 may be employed as long as a luminousintensity distribution pattern that satisfies the luminous intensitydistribution characteristic required of the LED indicator lamp can beachieved.

[0062] Also according to the present invention, the light emittingdiodes may be arranged according to such a simple rule as, for example,the number of light emitting diodes disposed on a horizontal linelocated above the optical axis is larger than the largest of the numbersof light emitting diodes disposed on horizontal lines located below theoptical axis, as long as the luminous intensity distributioncharacteristic required of the LED indicator lamp can be achieved.

[0063] The LED assembly 1 having the constitution described above isplaced at the bottom of the casing 2 so that a particular point (datumpoint) of the fundamental arrangement pattern is located on the axis ofthe casing 2 that has a truncated conical shape, namely the optical axisof the condenser lens 3. With this configuration, the luminous intensitydistribution pattern that satisfies the luminous intensity distributioncharacteristic required of the LED indicator lamp and the luminousintensity distribution pattern formed by the arrangement of the lightemitting diodes and the condenser lens 3 can be made substantiallyidentical with each other.

[0064] When the arrangement pattern of the light emitting diodes ismoved in the direction perpendicular to the optical axis of thecondenser lens 3, the luminous intensity distribution pattern generatedby the light emitted through the condenser lens 3 changes as theposition of the light emitting diodes changes. Therefore it is necessaryto align the condenser lens 3 and the LED assembly 1 so that theluminous intensity distribution pattern formed by the arrangement of thelight emitting diodes and the condenser lens 3 agrees with the luminousintensity distribution pattern that satisfies the luminous intensitydistribution characteristic required of the LED indicator lamp.

[0065] The luminous intensity distribution pattern formed by thearrangement of the light emitting diodes and the condenser lens 3 can bemade agree with the desired luminous intensity distribution pattern, bymoving the arrangement pattern of the light emitting diodes in thedirection perpendicular to the optical axis of the condenser lens 3,regardless of where the LED assembly 1 is located, either at the focusof the condenser lens 3, in the vicinity of the focus, before the focusor behind the focus.

[0066] That is, the LED indicator lamp of this embodiment achieves thedesired luminous intensity distribution pattern by setting thearrangement pattern of the light emitting diodes in the LED assembly 1in correspondence to the luminous intensity distribution pattern thatsatisfies the luminous intensity distribution characteristic required ofthe LED indicator lamp, and setting the relative positions of thecondenser lens 3 and the LED assembly 1 (determining the distancebetween of the condenser lens 3 and the LED assembly 1 and the positionof the LED assembly 1 in the plane perpendicular to the optical axis ofthe condenser lens 3) so that the luminous intensity distributionpattern formed by the arrangement of the light emitting diodes and thecondenser lens 3 agrees with the luminous intensity distribution patternthat satisfies the luminous intensity distribution characteristicrequired of the LED indicator lamp.

[0067] Since the distance between of the condenser lens 3 and the LEDassembly 1 is determined depending on the position of the LED assembly 1(arrangement pattern of the light emitting diodes) relative to theoptical axis of the condenser lens 3. Location of the LED assembly 1 isnot limited to a particular position. However, it is preferable tolocate the LED assembly 1 at the focus of the condenser lens 3, in thevicinity of the focus, or behind the focus for the reason describedbelow.

[0068] In the LED indicator lamp of this embodiment, the translucentcover 4 is provided in order to eliminate the unevenness in the lightintensity that varies with small period in space in the luminousintensity distribution pattern generated by the light emitted throughthe condenser lens 3. The unevenness in the light intensity that varieswith small period in space refers to the variations in the lightintensity with small period caused by the periodic arrangement of thelight emitting diodes. This variation causes the individual lightemitting diodes to be recognized as dots when the light emitted throughthe condenser lens 3 is directly observed, thus resulting indeterioration in perception.

[0069] In the LED indicator lamp of this embodiment, the translucentcover 4 has such a lens pattern as a plurality of lenses 41, 42 shown inFIG. 3 are periodically arranged on the inner surface of the translucentcover 4, in order to eliminate the unevenness in the light intensitythat varies with small period in space in the luminous intensitydistribution pattern of the light emitted through the condenser lens 3.

[0070] More specifically, each lens 41 has a concave surface 41constituted from a part of inner surface of a cylinder so that theincident light is diffused in the horizontal plane, while the concavesurface 42 is formed to incline from the vertical direction, so as todeflect the incident light downward.

[0071] Variation in light intensity with small period is eliminated byalternately arranging the lenses 41, 42 of different characteristics.

[0072] (Principle of Forming the Luminous Intensity Distribution Patternin the Embodiment)

[0073] Now the principle of forming the luminous intensity distributionpattern in this embodiment will be described in more detail below withreference to FIG. 4 through FIG. 8.

[0074]FIG. 4 through FIG. 8 are perspective views schematically showingthe luminous intensity distribution pattern corresponding to thearrangement pattern of the light emitting diodes. A plurality of thelight emitting diodes 11 are disposed in the horizontal direction on aplane (hereinafter referred to as emission plane) that includes a focalpoint 3 f located behind the condenser lens 3 and is perpendicular tothe optical axis 3 a.

[0075]FIG. 4 schematically shows a luminous intensity distributionpattern formed by light rays emitted by three light emitting diodes thatare arranged on a horizontal line located below the focal point 3 f ofthe condenser lens 3 in the emission plane, illustrated by way of animage 101 formed on an imaginary image plane 100 located in front of thecondenser lens 3.

[0076] As shown in FIG. 4, the image 101, formed by the light emitted bythe light emitting diodes that are located below the focal point 3 f ofthe condenser lens 3 in the emission plane, is located above the opticalaxis 3 a in the image plane 100. When the three light emitting diodesare moved downward in the emission plane, the image 101 moves upward inthe image plane 100.

[0077]FIG. 5 schematically shows a luminous intensity distributionpattern formed by light rays emitted by four light emitting diodes thatare arranged on a horizontal line including the focal point 3 f of thecondenser lens 3 in the emission plane, illustrated by way of an image102 formed on the image plane 100.

[0078] As shown in FIG. 5, the image 102, formed by the light emitted bythe light emitting diodes that are located on the horizontal line thatincludes the focal point 3 f in the emission plane, is observed as animage spreading vertically and horizontally around the intersect of theimage plane 100 and the optical axis 3 a in the image plane 100.

[0079]FIG. 6 schematically shows a luminous intensity distributionpattern formed by light rays emitted by five light emitting diodes thatare arranged on a horizontal line located above the focal point 3 f inthe emission plane, illustrated by way of an image 103 formed on theimaginary image plane 100 located in front of the condenser lens 3.

[0080] As shown in FIG. 6, the image 103, formed by the light emitted bythe light emitting diodes that are located above the focal point 3 f ofthe condenser lens 3 in the emission plane, is located below the opticalaxis 3 a in the image plane 100. When the five light emitting diodes aremoved upward in the emission plane, the image 103 moves downward in theimage plane 100.

[0081]FIG. 7 schematically shows a luminous intensity distributionpattern formed by light rays emitted by six light emitting diodes thatare arranged on a horizontal line located above the focal point 3 fhigher than in the case of FIG. 6 in the emission plane, illustrated byway of an image 104 formed on the imaginary image plane 100.

[0082] As shown in FIG. 7, when the light emitting diodes are placedhigher than in the case of FIG. 6 in the emission plane, the image 104is formed further lower than in the case of FIG. 6 in the image plane100.

[0083]FIG. 8 shows an image 110 formed on the image plane 100 when thelight emitting diodes of the arrangements shown in FIG. 4 through FIG. 7are all arranged in the emission plane.

[0084] In this case, the image 110 is formed by overlapping of images101, 102, 103 and 104 formed by the light emitting diodes arranged alongeach horizontal line as schematically in FIG. 8.

[0085] As shown in FIG. 8, when the light emitting diodes are disposedin such an arrangement as the number of light emitting diodes disposedalong a horizontal line that is located above is larger than the numberof light emitting diodes 11 disposed along a horizontal line that islocated below in the emission plane, and the light rays emitted by theplurality of light emitting diodes arranged as described above areoutput through the condenser lens 3, light spreads in the horizontaldirection more widely in the upper field than the spread of light in thehorizontal direction in the lower field.

[0086] When the arrangement pattern of the light emitting diodes 11shown in FIG. 8 is moved upward as a whole, the image 110 moves downwardin the image plane 100. When the arrangement pattern is moved downwardas a whole, the image 110 moves upward in the image plane 100.

[0087] In other words, light can be deflected downward by moving thearrangement pattern upward in the emission plane, and light can bedeflected upward by moving the arrangement pattern downward in theemission plane.

[0088] Similarly, light can be deflected to the left by moving thearrangement pattern to the right in the emission plane, and light can bedeflected to the right by moving the arrangement pattern to the left inthe emission plane.

[0089] Thus since the luminous intensity distribution characteristic isachieved by overlapping of the luminous intensity distributioncharacteristics of the light emitting diodes arranged in the individuallines, the overall luminous intensity distribution characteristic mayinclude a portion of lower light intensity around the luminous intensitydistribution pattern indicated with numeral 110 a in FIG. 8.

[0090] In such a case, the unevenness in the light intensity can besmoothed by placing an additional light emitting diode at a position inthe emission plane corresponding to the portion 110 a. The lightemitting diode 11 a shown in FIG. 2 is provided for the purpose ofachieving a luminous intensity distribution pattern similar to thedesired luminous intensity distribution pattern by smoothing theunevenness in the light intensity.

[0091]FIG. 9 is a graph of light intensity distribution in an imageplane for an example of luminous intensity distribution characteristicin case the light emitting diodes are arranged as shown in FIG. 2.

[0092] Data shown in FIG. 9 were obtained by measurement using acondenser lens 300 nm in diameter having focal length of 120 mm andlight emitting diodes arranged in a plane that includes the focal pointof the condenser lens 3 and is perpendicular to the optical axis.

[0093] Luminous intensities in the regions shown in FIG. 9 are asfollows:

[0094] Region enclosed by line 51: 600 candelas or higher

[0095] Region enclosed by line 51 and line 52; from 550 to 600 candelas

[0096] Region enclosed by line 52 and line 53; from 500 to 550 candelas

[0097] Region enclosed by line 53 and line 54; from 450 to 500 candelas

[0098] Region enclosed by line 54 and line 55; from 400 to 450 candelas

[0099] Region enclosed by line 55 and line 56; from 350 to 400 candelas

[0100] Region enclosed by line 56 and line 57; from 300 to 350 candelas

[0101] Region enclosed by line 57 and line 58; from 250 to 300 candelas

[0102] Region enclosed by line 58 and line 59; from 200 to 250 candelas

[0103] Region enclosed by line 59 and line 60; from 150 to 200 candelas

[0104] Region enclosed by line 60 and line 61; from 100 to 150 candelas

[0105] Region enclosed by line 61 and line 62; from 50 to 100 candelas.

[0106] When it is desired to make the light intensity higher in aparticular direction, density of the light emitting diodes in theportion of the arrangement pattern corresponding to the direction may beincreased as will be described in a variation of the embodiment.

[0107] As described above, the LED indicator lamp according to theembodiment of the present invention can achieve the desired luminousintensity distribution pattern with a simple constitution, by employingthe condenser lens 3 and arranging the light emitting diodes in thearrangement pattern that corresponds to the desired luminous intensitydistribution pattern.

[0108] Also the LED indicator lamp according to the embodiment of thepresent invention allows it to change the direction of light emission(direction in which the light intensity is highest) while maintainingthe basic luminous intensity distribution pattern, by changing therelative positions of the substrate whereon the plurality of lightemitting diodes are arranged in the predetermined arrangement patternand the condenser lens 3.

[0109] Variation

[0110] An LED indicator lamp of a variation of the present invention isconstituted similarly to the LED indicator lamp of the embodiment exceptfor changing the arrangement pattern of the light emitting diodes 11, 11a on the substrate 12.

[0111] In the LED indicator lamp of this variation, density of the lightemitting diodes 11 disposed below a horizontal 14 that crosses theoptical axis at right angles is made higher than the density of thelight emitting diodes 11 disposed below the horizontal 14.

[0112] This constitution makes it possible to increase the lightintensity in a particular portion that corresponds to the portion ofhigh density in the arrangement pattern, thereby to achieve the desiredintensity distribution in the luminous intensity distribution pattern incorrespondence to the density of the arrangement pattern.

[0113] Also according to the present invention, spaces between adjacentlight emitting diodes can be changed for the light emitting diodesdisposed in the horizontal direction as shown in FIG. 11.

[0114] This makes it possible to change the light intensity distributionfrom the right to the left of the center in correspondence to the spacebetween adjacent light emitting diodes.

[0115]FIG. 11B is a graph showing the situation described above. In FIG.11B, light intensity distribution from the right to the left of thecenter is indicated schematically by solid line 120 when the spacebetween the light emitting diodes located away from the center is madelarger than the space between the light emitting diodes located near thecenter as shown in FIG. 11A.

[0116] In FIG. 11B, light intensity distribution from the right to theleft is indicated schematically by dashed line 121 when the lightemitting diodes are disposed with uniform density on the horizontal linefor the purpose of comparison.

[0117] As will be clear from FIG. 11B, it is made possible to change thelight intensity distribution from the right to the left of the center incorrespondence to the space between adjacent light emitting diodes.

[0118] In the example shown in FIG. 11A, spaces between adjacent lightemitting diodes disposed in the horizontal direction are changed.However, the present invention is not limited to this constitution andspaces between adjacent light emitting diodes disposed in the verticaldirection may also be changed.

[0119] This makes it possible to change the light intensity distributionin the vertical direction around the center in correspondence to thespace between adjacent light emitting diodes.

[0120] As will be made clear from the above description of theembodiment and the variation, the LED indicator lamp of the presentinvention achieves the desired luminous intensity distribution patternby employing the condenser lens 3, the arrangement pattern of theplurality of light emitting diodes and the relative positions of thearrangement pattern and the condenser lens 3. Therefore, desiredluminous intensity distribution patterns can be easily achieved to meetvarious requirements, by changing the density of the light emittingdiodes in the arrangement pattern depending on the position, changingthe space between adjacent light emitting diodes in the horizontaldirection or the space between adjacent light emitting diodes in thevertical direction, in accordance to the desired luminous intensitydistribution pattern to be achieved with the LED indicator lamp.

[0121] In the embodiment and the variation, the desired luminousintensity distribution pattern is achieved by means of the arrangementof the plurality of light emitting diodes and the condenser lens 3.However, the present invention is not limited to this constitution andthe desired luminous intensity distribution pattern may also be formedby providing a lens pattern formed on the translucent cover 4 inaddition to the plurality of light emitting diodes and the condenserlens 3.

[0122] Also in the embodiment and the variation, the arrangement patternis constituted by arranging the plurality of light emitting diodes alonghorizontal lines in a plane perpendicular to the optical axis of thecondenser lens 3, but the present invention is not limited to thisconstitution.

[0123] Specifically, when light emitting diodes 71, 72 are arranged in aplane perpendicular to the optical axis of the condenser lens 3 (FIG.12B), images 71 a, 72 a are formed on a screen in correspondence to thelight emitting diodes 71, 72 (FIG. 12A).

[0124] In case the light emitting diode 72 is located before the planeperpendicular to the optical axis of the condenser lens 3 (the planewhere the light emitting diode 71 is placed) as shown in FIG. 13B, incontrast, image 72 b of the light emitting diode 72 on the screen isspread to be larger than the image 72 a shown in FIG. 12A, as shown inFIG. 13A.

[0125] Therefore, a luminous intensity distribution pattern that isspread in the horizontal direction can be formed as indicated by theimage 70 in FIG. 14A, by placing the light emitting diode 71 at thefocal point of the condenser lens 3 and arranging the light emittingdiodes 72, 73 at advanced positions according to the distance from thelight emitting diode 71 to the left and right (FIG. 14B).

[0126] Thus according to the present invention, a luminous intensitydistribution pattern that corresponds to the inclination of the planewhere the light emitting diodes are arranged or to the three-dimensionalarrangement of the light emitting diodes can be achieved, by incliningthe plane where the plurality of light emitting diodes are arranged (sothat the plane does not perpendicularly cross the optical axis of thecondenser lens 3) or arranging the plurality of light emitting diodes inthree-dimensional arrangement.

[0127] Three-dimensional arrangement of the light emitting diodes may besuch as the light emitting diodes are disposed on the inner surface of asphere, the light emitting diodes are disposed on the external surfaceof a sphere, or the light emitting diodes are disposed on two or moreplanes that cross each other.

[0128] As described in detail above, the present invention is capable ofsatisfying requirements for wide varieties of luminous intensitydistribution characteristics by setting all or part of the components inaccordance to the desired luminous intensity distribution pattern.

[0129] The LED indicator lamp of the present invention is capable ofachieving the desired luminous intensity distribution pattern in orderto meet wide varieties of requirements, and can therefore be applied toindicating lamps for various applications such as traffic lamp.

1. A LED indicator lamp which has a luminous intensity distributioncharacteristic comprising; a plurality of light emitting diodes and acondenser lens, wherein said plurality of light emitting diodes arearranged in a pattern that corresponds to a luminous intensitydistribution pattern that is set based on said luminous intensitydistribution characteristic, while said light emitting diodes and saidcondenser lens are arranged so that the luminous intensity distributioncharacteristic is achieved by the light that is emitted by the pluralityof light emitting diodes and output through the condenser lens in theluminous intensity distribution pattern.
 2. The LED indicator lampaccording to claim 1; wherein said plurality of light emitting diodesare located at the focus of said condenser lens or in the vicinitythereof.
 3. The LED indicator lamp according to claim 1; wherein saidplurality of light emitting diodes are arranged on a plane that crossesthe optical axis at right angles at the focus of said condenser lens orin the vicinity thereof.
 4. The LED indicator lamp according to claim 1;wherein said plurality of light emitting diodes are arranged on a planethat crosses the optical axis obliquely at the focus of said condenserlens or in the vicinity thereof.
 5. The LED indicator lamp according toclaim 1; wherein said plurality of light emitting diodes are distributedin a three-dimensional arrangement at the focus of said condenser lensor in the vicinity thereof.
 6. The LED indicator lamp as in one ofclaims 1 to 5; wherein said condenser lens is a Fresnel lense.
 7. TheLED indicator lamp as in one of claims 1 to 6; wherein said plurality oflight emitting diodes are disposed in such an arrangement as the numberof light emitting diodes located above the optical axis is larger thanthe number of light emitting diodes located below the optical axis. 8.The LED indicator lamp as in one of claims 1 to 7; wherein saidplurality of light emitting diodes are disposed in such an arrangementas the light emitting diodes are distributed in one portion with adensity different from that in other portions.
 9. The LED indicator lampas in one of claims 1 to 8; wherein said plurality of light emittingdiodes include one or more light emitting diodes that are intended tocorrect unevenness in the light intensity distribution of the luminousintensity distribution pattern produced by the light emitted through thecondenser lens.
 10. The LED indicator lamp as in one of claims 1 to 9;wherein said plurality of light emitting diodes are disposed in such anarrangement as the light emitting diodes are placed in at least oneportion at intervals different from the intervals between light emittingdiodes in other portion.
 11. The LED indicator lamp as in one of claims1 to 10 further comprising a translucent cover placed in front of thecondenser lens.
 12. The LED indicator lamp according to claim 1; whereinsaid translucent cover has a lens pattern formed thereon so as to smoothout the periodic intensity distribution generated by the periodicarrangement of said light emitting diodes.
 13. A LED indicator lampwhich has a luminous intensity distribution characteristic comprising; aplurality of light emitting diodes, a condenser lens placed in front ofthe plurality of light emitting diodes and a translucent cover with alens pattern formed thereon being placed in front of the condenser lens,wherein said plurality of light emitting diodes are arranged in apattern that corresponds to a luminous intensity distribution patternthat is set based on said luminous intensity distributioncharacteristic, wherein said light emitting diodes, said condenser lensand said translucent cover are arranged so that the luminous intensitydistribution characteristic is achieved by the light that is emitted bysaid plurality of light emitting diodes through the condenser lens andsaid translucent cover in the luminous intensity distribution pattern.14. The LED indicator lamp according to claim 13; wherein said lenspattern formed on the translucent cover are formed so as to smooth outthe periodic intensity distribution generated by the periodicarrangement of said light emitting diodes.